Transverse driving bodies, particularly airplane wings

ABSTRACT

This invention relates to a transverse driving body, particularly an aircraft wing, the wing comprising a wing tip extending basic parts of the wing in the span direction for the purpose of increasing the aspect ratio, the wing tip being of triangular design with a sweptback leading edge, and the profile camber of each of the wing tip increasing at least over a portion of the extension thereof from a basic wing part to the wing tip.

This is a continuation application, of application Ser. No. 347,222,filed Feb. 9, 1982, which in turn was a continuation of application Ser.No. 116,562, filed Jan. 29, 1980, both are now abandoned.

This invention concerns transverse driving bodies, particularly airplanewings.

Efforts are widely being made at present in the field of aviation, toimprove the economy of aircraft on account of rising fuel costs. One wayof achieving this is to decrease the drag. The term "aircraft drag"comprises a number of various causes. One of these is, for instance, thesurface friction in general. Other factors are interference drag,profile drag or also the lift-dependent induced drag which is the basisof the invention.

The performance of civil aviation aircraft, for instance rate of climband range, can be improved by using aircraft wings of larger span oraspect ratio. However a substantial problem is encountered in thatincreasing the aspect ratio also appreciably increases the wing weight,whereby the advantages are cancelled again. As regards wings withconventional edges along the direction of flow, increasing the aspectratio as a first approximation results in an increase in weightproportional to the increase in the aspect ratio (proportional to thesquare of the increase in span).

The object of the present invention is an improvement in aircraftperformance by design measures at the wing for the purpose of reducingthe lift-dependent drag by means of an enlarged wing aspect ratio for amuch reduced increase in weight. The problem is solved by the inventionin that the aircraft wing comprises a wing tip part extending the basicwing parts in the direction of the span for the purpose of increasingthe aspect ratio, in that the wing tip parts are triangular with asweptback leading edge, and in that the profile camber of the wing tipparts increases from the basic wing part to the wing tip at least overpart of its size. The profiles of the wing tip parts are of such adesign that their local direction of zero lift does not vary withrespect to the end of the basic wing part.

This design of the invention for aircraft wings achieves that for agiven lift, the total drag for equal wing load is considerably lessenedwith respect to wings with conventional wing tips. While the increase inaspect ratio also results in an undesired increase in wing weight, it ishowever substantially less compared with conventionally designed wingtip parts. The advantage so achieved is due to the special design of thewing tip part causing a change in the distribution of lift across theentire wing span. This change essentially resides in a shallowerdecrease of the curve of the lift distribution toward the wing tips. Asa result, there is a lesser root flexural moment than in conventionalwings of the same aspect ratio due to the lighter structure of theoverall wing. The increase in the local lift coefficient due to thesweepback of the invention in the leading edge at the wing tip part andthe resulting premature flow separation from the wing tip parts withrespect to the flow at the basic wing is counteracted according to theinvention by the change in profile camber and additionally of the noseradius in connection for constant direction of zero lift. Thetheoretically induced drag at the wing and the total drag can besubstantially decreased by the increase in aspect ratio. The saving inweight compared to a conventionally formed wing extension to the sameaspect ratio amounts to about 75%. Design and manufacture of the wing ofthe invention require no additional expenditure as compared with knownwings.

A further embodiment of the invention provides that the local zero liftdirection of the wing tip parts remains constant from the junctionalcross-sections between the basic wing parts and the wing tip parts. Sucha design avoids increasing the induced drag for a given lift in theregion of the wing tip parts.

Because of the special design by which the wing tip parts enclose anangle of about 45° by their junction cross-sections to the basic wingparts and the associated leading edge, a reduction in the induced dragis obtained compared to conventionally designed wing tip parts.

A further advantageous embodiment of the main concept of the inventionresides in the increase in the radius of the profile nose of the wingtip parts corresponding to the increase of the profile camber of theseparts. As shown by research, the flow separation in the range of largeangles of attack begins at the outermost section of the wing tip parts.The special design of the profile nose and profile camber of the wingtip parts allows extending the range of flow applied to these parts upto relatively high angles of attack.

By mounting the wing tip parts to the basic wing parts in the sense ofincreasing the aspect ratio and by making the profiles of both kind ofparts merge continuously into each other, both a simpler construction isobtained regarding the junction between basic wing part and wing tippart and a more favorable control of the flow as regards the separationbehavior, on account of the continuous transition from one contour tothe other.

Lastly, because the trailing edge of the wing tip parts is a rectilinearcontinuation of the trailing edge of the basic wing parts, a substantialsaving in weight is achieved without thereby adversely affecting thelift behavior.

The drawings show one embodiment of the invention, which is describedbelow.

FIG. 1 is a top view of an aircraft with triangular wing tip parts,

FIG. 2 is a top view on a much larger scale than FIG. 1 of one of thetriangular wing tip parts, and

FIG. 3 is a series of profile cross-sections along given spacings in thewing tip parts along lines III₁ --III₁ ; III₂ --III₂ ; and III₃ --III₃.

FIGS. 1 through 3 show an aircraft wing 2, the wing halves 3 of whichare mounted by means of the wing root 4 to the aircraft fuselage 1 inthe manner of a high wing plane. The junction of the wing halves 3 tothe plane fuselage is of conventional design.

The wing tip parts 6 are joined by the end ribs 7 to the basic wingparts 9 (FIG. 2) for the purpose of extending the wing span, thejunctional cross-section 10 being vertical and orthogonal to the wingspan Fs.

The leading edge 13 of the wing tip parts 6 sweeps back at an angle ofabout 45° starting from the leading edge 12 of the basic wing part 9 andmerges by the transition arc 15' and 15 into the trailing edge 16 andthe wing leading edge 12 respectively of basic wing part 9. It can thusbe seen, that each of the basic wing parts 9, has a leading edge, whichin relation to the wing span direction has an angle, that issignificantly smaller than the 45° sweep back angle of the leading edge13, of the respective connected wing tip part 6. Starting from thetrailing edge 16 of the wing tip parts 6, the profiling, in extension ofthat of the overall wing 2, can extend in the direction of the wing tipas far as a terminal profile line "a" shown in dash-dot manner in FIG.2. The wing upper and lower surface is respectively denoted by 20 and 21in FIG. 3.

As indicated by the individual profile sections in FIG. 3, the profilecamber and the nose radius r, r', r" increase from the basic wing part 9toward the wing tip, i.e., the profile camber, and nose radius increase.The increase in camber and nose radius applies in the direction of thewing span as far as a vertical cross-sectional plane b indicated indash-dot manner in the direction of the chord. From this cross-sectionalplane b, the profile camber and the relative nose radius r" remainconstant to the wing tip and the local zero lift direction is unchanged.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:
 1. An aircraft wing comprising:a basic wing part,having a leading edge and a trailing edge and being essentially ofunswept configuration; wing tip means for extending the span of thebasic wing part so as to increase the aspect ratio as compared with awing contoured as the basic wing part with similar wing area, the wingtip means being significantly shorter than the basic wing part, andbeing of triangular design with a swept back leading edge having anangled of about half a right angle in relation to the wing spandirection, said angle being larger than an angle between the leadingedge of the basic wing part and the direciton of the wing span, the wingtip means extending in span direction for about a chord length of thewing at the junction between the basic wing part and the wing tip means;the wing section camber of said wing tip means increasing at least overa portion of the extension thereof from the basic wing aprt to the tipof the triangular wing tip means; and the local zero lift direction ofthe wing tip means remaining constant beginning at the junctioncross-section between the basic wing part and the wing tip means.
 2. Awing according to claim 1 in which the radius of the profile nose of thewing tip means increases at least in part over the extension thereof inthe span direction from the basic wing part.
 3. A wing according toclaim 2, in which the increase in the radius of the profile nose of thewing tip means corresponds to an increase in camber of the profile ofsaid wing tip means.
 4. A wing according to claim 1, in which thetrailing edge of said wing tip means extends outwardly and rectilinearlyas a continuation of the trailing edge of the basic wing part.